Solid electrolytic capacitors (e.g., tantalum capacitors) have been a major contributor to the miniaturization of electronic circuits and have made possible the application of such circuits in extreme environments. An example of a solid state capacitor and related mass production method for manufacturing surface mountable solid state capacitors is disclosed in U.S. Pat. No. 5,357,399 to Salisbury.
Some solid electrolytic capacitors have an anode lead formed of a substantially planar surface that is bonded to an anode body with a seed/seeding layer. Seed layers, and sometimes the anode bodies as well, have been formed as respective continuous planes of material that are cut in multiple dimensions to provide discrete capacitor elements. For example, U.S. Pat. No. 6,699,767 to Huntington discloses a method for manufacturing multiple solid state capacitors that includes steps for forming such seed and anode components. An entire upper surface of a wafer has sintered thereon a seed layer, for example a dispersion of tantalum powder. A green (i.e. un-sintered) mixture of fine-grained capacitor grade tantalum powder is then pressed onto the upper surface of the substrate to form a green layer. The green layer is sintered to fuse the fine grained powder into an integral porous network. The sintering process also fuses the porous layer to the coarse seeding layer. The substrate assembly is then machined to produce an orthogonal grid of transverse channels and longitudinal channels, which are cut to a depth just beyond the level of the porous tantalum layer so that the cuts impinge on the substrate. The machining process produces an array of orthogonal section bodies, on the substrate, which are ultimately processed to form the anode portions of the capacitors.
In a related variation to the above manufacturing process, a continuous plane of material forming a seed layer is formed over the substrate and sintered. Subsequently, anodes of the same or varying heights are matrix pressed onto the seeded wafer. After pressing, the anodes are sintered. A series of orthogonal cuts must still be performed through the seed layer slightly into the wafer to remove the seed from between respective anode layer bodies and form discrete capacitor elements.
The multiple steps for forming discrete capacitor elements, especially the cutting steps in U.S. Pat. No. 6,669,767 to Huntington to produce the transverse and longitudinal channels, can be a time-consuming and expensive part of the manufacturing process. In addition, generally thicker substrates are required so that the channels can be cut into the substrate beyond the level of the porous tantalum layer thereon, thus limiting potential volumetric efficiency of the capacitor elements. As such, a need currently exists for an improved capacitor element having a decreased height profile and increased volumetric efficiency that can be produced in a simplified, more cost-efficient process.